Master Thesis - Hochschule Bonn-Rhein-Sieg

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2. Overview on human-robot Master Thesis Björn Ostermann page 10 of 126 2 Overview on human-robot collaboration 2.1 State of the art Since the invention of the joint arm robot in 1954 by George Devol, founder of the company Unimation, and its first usage in 1962 by General Motors [64], humans have been separated from industrial robots to assure their safety. Until the end of the 20 th century this separation was achieved by rigid fences. A major step towards a fenceless workplace was achieved in 1996, when the sourcecode SICK programmed for lasercannes was approved or safety related applications [60] by the BGIA, and later in 1998, when the first laser scanner, the PLS 101-312 by SICK, was approved for safety related applications [60] by the BGIA. The next step was achieved in 2006, when the company Pilz GmbH & Co. KG introduced a system, called SafetyEye [47], which is based on cameras (see Figure 1). With respect to safety, both systems, laser scanner and SafetyEye, can differentiate between three different situations. Therefore their field of view can be separated into non protective and protective fields. The protective field thereby is separated into a warning and a safety area. If there is no object in the protective field, the robot is fully functional. If an object enters the warning (yellow) area, the speed of the robot is reduced, and if an object enters the safety (red) area, the robot is stopped. In case of the SafetyEye, no action is taken for objects in the working (blue) area, since intruding objects can not be distinguished from working material or the robot itself. Although laser scanner and cameras allow easy changes of these boundaries between production cycles, during production the human and the robot are still separated by a nonflexible invisible fence, and no real collaboration is possible. SafetyEYE Protective Field Robot Robot’s working space Figure 1: Pilz SafetyEYE - an invisible fence [47]
2. Overview on human-robot Master Thesis Björn Ostermann page 11 of 126 2.2 State of science – Related Work The first approaches on safe interactions of humans and industrial robots were made in the 80s. After the first death of a worker related to a robot accident, reported in 1982 [1], safety studies in 1983 concluded that a robot could only be safe if the robot could detect the approach of a human and react accordingly [2]. In 1985 [3] Graham and Meagher of the Rensselaer Polytechnic Institute in New York investigated microwave, ultrasound, infra-red and capacitive sensors on their applicability in collaborative workplaces. They continued their work, together with Derby, in 1986 [4] resulting in the conclusion that “much research still needs to be done on robotics safety”. The Rensselaer Polytechnic Institute is still working in the field of safe robot-human collaboration. In one of their latest projects from 2007 [5] Meisner, Isler and Trinkle used a galvanic skin response sensor, measuring the workers stress level, to generate robot trajectories. In 1989 [6] Takakura et al. outfitted a robot with torque sensors and programmed an algorithm that worked on contact sensing and memorization of objects. Although this approach was not feasible in praxis, due to the reduced speed of the robot, in order to avoid any damage by collisions, and problems with dynamic objects, whose changed positions can not be tracked, the idea of using torque sensors persists until today (see chapter 2.2.2). In 1992 and 1994 Novak and Feddema used capacity sensors for object avoidance [7]. The advantage of this approach is that the robot does not need to touch the obstacle, but can sense it in its vicinity. While increasing the sensor range from touch to close vicinity was an improvement, the problem in this approach is the different reactions of capacity sensors to different materials. Ebert and Henrich presented in 2002 a solution that used a multiple camera system to detect collisions between the robot and obstacles [10]. The problems they reported for this approach existed in cells being reported as occupied while free and vice versa and in the robot blocking the view of the cameras in certain positions. In later projects by Henrich this problem has been reduced but not completely solved (see chapter 2.2.3). Heiligensetzer and Wörn demonstrated in 2002 [20] [21] a Kuka Robot, equipped with capacity proximity sensors and haptic devices. Heiligensetzer continued the approach, using capacitive proximity and tactile sensors, in 2004 [19] and 2007 [57]. A problem in approaches using force sensors is always the reduced speed of the robot, which is necessary to avoid harm to humans. The robot presented in 2007 was therefore also equipped with collision absorbing material, making it possible to detect a collision before harm is done to the worker. Wörn continued his work in this field in 2004 [22], together with Yigit and Burgart, by developing a reflex based control for industrial robots, in which reflexes take over the control if a dangerous situation is detected.
Page 1 and 2: Master Thesis ”Industrial jointed
Page 3 and 4: Statutory Declaration Master Thesis
Page 5 and 6: Contents Master Thesis Björn Oster
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Page 19 and 20: 3. Hard- and software Master Thesis
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5. Algorithms Master Thesis Björn
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7. Conclusion and Outlook Master Th
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8. Bibliography Master Thesis Björ
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9. List of Figures Master Thesis Bj
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9. List of Figures Master Thesis Bj
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Master Thesis - Hochschule Bonn-Rhein-Sieg

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